- SeaMonkey can be set as default client/browser on Mac and Linux now- The new IonMonkey compiler improves JavaScript performance- Preliminary support for WebRTC has been added- Image quality has been improved through a new HTML scaling algorithm- CSS3 Flexbox has been implemented- Support for new DOM property window.devicePixelRatio has been added- Support for @supports has been added (disabled for now)- Startup time has been improved through smart handling of signed extension certificates- HTML5: Support for W3C touch events has been implemented, taking the place of MozTouch events- Insecure content loading has been disabled on HTTPS pages- Responsiveness for users on proxies has been improved- Fixed several stability issues